The Grocer, carries out a weekly mystery shopping basket survey checking the prices of 33 everyday items at the five major supermarket chains - but this week they included Aldi too.

Next came Sainsbury's at £39.51 which was £6.37 more expensive than Aldi followed by Tesco, Morrisons and Waitrose.

The Grocer said: "Guest retailer Aldi claimed a convincing win over its traditional supermarket rivals this week - and in doing so illustrated one of the key reasons why Asda and Sainsbury’s feel the need to merge.

"Aldi’s £33.14 total was £4.41 cheaper than Asda, helped by offering the lowest price for 27 of the 33 items on our list.

HOW DO THE SHOPPING BASKETS COMPARE?

THE Grocer sent a secret shopper to six suprmarkets to buy 33 everyday items to see how prices compare. Here are the results:

Aldi - £33.14

Asda - £37.55

Sainsbury’s - £39.51

Tesco - £40.70

Morrisons - £41.68

Waitrose - £48

"Twenty three of these were exclusively cheaper than any of its rivals.

"This makes Asda 13.3 per cent more expensive and while the gap has closed from 16.5 per cent in January, drastic measures appear to be needed if Asda is to genuinely close the price gap to the discounters."

Sainsbury's managed to grab third spot with £39.51 but still it was £6.37 more expensive than Aldi.

The Tesco shop cost £40.70, and a whopping £7.56 more expensive than the budget retailer, and said it's price guarantee scheme didn't make much of a difference as the list focused on own brand products.

Their shopper had 45p taken off her bill at the checkout which still left it £7.11 more expensive than Aldi.

Morrison was £11.46 more expensive and unsurprisingly, Waitrose had a difference of £14.86 more on the discounter's grocery bill.

When they carried out the test, Waitrose only had two of the products on offer, compared to Asda's nine, Aldi's eight, Morrisons' six and four each at Sainsbury's and Tesco.

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